1. Technical Field
Embodiments of the present disclosure generally relate to semiconductor integrated circuits and, more particularly, to period signal generation circuits.
2. Related Art
Integrated circuits (ICs) including semiconductor memory ICs may need periodic signals to control internal operations thereof. That is, the ICs may execute the internal operations in response to the periodic signals which are generated in the ICs or from an external device. The periodic signal may include pulses which are created to have a uniform cycle. Thus, the periodic signal may be used to execute iterative internal operations of the ICs.
Volatile memory devices, for example, dynamic random access memory (DRAM) devices may lose their stored data as the time elapses even though their power supplies are continuously provided. Thus, all the memory cells in the DRAM devices should be refreshed within a data retention time corresponding to a maximum time that the memory cells can retain data. Since the refresh operation is periodically executed, the DRAM devices may need the periodic signals to execute the refresh operation.
Operation speeds of the semiconductor devices may vary according to a temperature. That is, the higher the temperature is, the slower the operation speed of the semiconductor devices is. In contrast, the lower the temperature is, the faster the operation speed of the semiconductor devices is. If the operation speed of the semiconductor devices varies according to the temperature, the reliability of the semiconductor devices may be degraded to cause malfunction.